Muhammad vs. Laila Ali. He bobs, she weaves. She lunges, he feints. She's young. And so is he. He's wily. And so is she. Their feet are quick, their eyes are bright.

It's the best fight the boxing world has seen in years, and it never happened. Except, of course, in the minds and through the magic of the folks who bring us "Impossible is Nothing," the latest ad campaign from adidas.

The best fight we've seen in years.

You've seen it, right? You've felt the goosebumps, done the shuffle, and maybe thrown a few shadow punches at the file cabinets, right?

Want to know how they did it? Like this:

"Ali is the icon of all icons in sports," says Peter McHugh, creative director of 180, the Amsterdam-based agency that produced the ad. "We knew we wanted to begin with him."

The idea for the campaign was to invoke adidas' storied history (Ali wore adidas boots in several key fights, including the Rumble in the Jungle) and at the same time build a bridge to its present-day athletes (enter Laila).

The team at 180 began by watching every scrap of Ali film they could get their hands on. "We didn't want a full-on fight between Muhammad and Laila," says writer Richard Bullock. "So we were looking for sequences where Ali had his gloves down and was avoiding punches rather than throwing them."

They settled on sequences from four fights: His 1960 Olympic gold medal bout in Rome; a fight against Cleveland Williams in November, 1966; the notorious "what's my name" dismantling of Ernie Terrell in February, 1967; and the classic 1971 rope-a-doping of George Foreman in Kinshasa, Zaire.

Rome is the establishing shot, swooping down on the ring from above. Bits of the Foreman fight -- Ali's entrance into the ring and the wink he gives Laila at the end -- frame the spot. The action sequences in between are taken from the Williams and Terrell bouts.

"He wore the same wardrobe in those fights, and they were both held in the Houston Astrodome," producer Cedric Gairard says. "There was enough continuity that we were able to choreograph bits from each of them in sequence and produce a short film much like what you see of Ali in the finished product."

Laila looking quite comfortable in the shoot.

After untold dollars, pleadings and promises, rights to the film clips were secured. The next task was to prepare the footage for Laila's entrance.

"We had to remove the people who were already in the frame," says Fred Raimondi, visual effects supervisor for Digital Domain, and chief tech wizard on last year's dazzling "23 vs. 39" Michael Jordan Gatorade ads. "In the original footage of the opening of the Williams fight, for example, the referee and the opponent's entourage were in the center of the ring."

Layering various angles and images, and digitally producing canvas, ropes, and members of the ringside audience, Raimondi's team painstakingly erased the extras crowding up the screen.

Next came new live-action sequences of Laila climbing through the ropes and shrugging off her robe. The costumes are borrowed from Will Smith's "Ali." The cameras in reporters' hands are vintage.

"That's the most challenging thing," Bullock says. "To get the authentic footage to match the new footage; to make it seem as though the two places are one."

And then came the truly heavy lifting: Replacing Williams and Terrell with Laila. It wouldn't be enough to have her simply jab and move. She had to reproduce their movements and punches, but exactly. Otherwise, Ali's reactions would make no sense, and the two fighters would look like they were nowhere near each other.

"We wanted the interplay between father and daughter to be seamless," McHugh says.

The job of making that happen fell to Raimondi and director Lance Acord, who had done camera work on "Being John Malkovich" and "Adaptation."

"We made a tape of the original fighter boxing a particular move over and over again," Raimondi says. "And then attached a snare drum hit to the point of full extension on each of the original boxer's punches."

The snare drum hits, a kind of bambambam-bam metronome, were Laila's guide to timing and feeling the moment as the cameras rolled.

George Foreman could've used this technology to fight Ali back in the day.

"The human animal is really good at rhythmic things," Raimondi says. "This way, Laila was able to concentrate on her target and time her punches perfectly."

Sometimes, her target was a tennis ball atop a head-high pole. Sometimes, it was a body-double, hired because he had boxing experience and could mimic Ali's original moves, and kept on because Laila felt his back and shoulders looked sufficiently like her Pop's. She and her two opponents worked against a green screen for the fight sequences. Her live-action punching and dancing, plus from-scratch scenes of her approaching and entering the ring, were then layered over and into the short film of Ali with which the process began.

"It's called compositing," Raimondi says. "You take the moving images and layer them together so it looks like one thing is happening with another."

Everything from there is meticulous detail work.

Make sure the new Laila footage has the same gritty look of the original Ali footage. They shot the new stuff at a cinematically-high resolution to maintain the integrity of their composite work; and then, says Gairard, they "downgraded it to match the look and feel of the original."

Digitally add or subtract bits of a referee's shirt or a fan's hat, depending on how Laila's body matched up with Williams' or Terrell's.

Tweak the lighting and color to look the way it did back in Ali's day, when cameras weren't as sophisticated and film wasn't as durable.

"We finished filming Laila in October," McHugh says. "But there were two whole months of tweaking and perfecting in post-production."

Every little change, in fact, required a 20-hour rendering period before the digital images were fully adjusted and ready for further work.

Like father, like daughter.

"It wasn't like a commercial," Raimondi says. "It was like prepping a movie. It was fantastic."

Amen, Fred. It was and it is.

So those are the guts.

And why do they it hit us in the gut, so hard and so true?

For starters, because new tech in the service of something as simple and basic as two bodies dancing and jousting in space -- and not of something simply techy -- is a hyper-real rush.

Because there's love in the spot: His for her, hers for him, and ours for him, too.

Because it's bedrock generational stuff -- fathers and daughters going heads-up for familial supremacy. Everybody watching has some version of this battle in their history and their homes. To see it played out, just as common as you please, between The Greatest of All Time and his bad-ass daughter is charming and human.

Because the voice-over works. Voice-over is a dark, perilous land. Many a worthy project has shriveled up and died in voice-over land. (Remember "Blade Runner," friends.) And yet, somehow it's right in this spot. Maybe it's the marriage between the rising guitar chords and Laila's genuine intensity. Maybe it's the fact that she speaks for Ali, whom we know is nearly silent now.

Whatever. It works.

Because more than watching him punch, which any fighter could do and some could do better than he could, we love watching Ali dance. And when he slips four of her punches without lifting an arm, we miss him and marvel at him as much or more than we ever have before.

Because on some level, the spot isn't about nostalgia at all, but about a new thing. Once, it was his; this time, it's her new thing. You see this in her head roll, when the robe hood slips off and away. And you see it in her smile at his wink. You're not looking at manufactured confidence. You're looking at something deep and inbred, something that might strike you as funny and out of place -- women's boxing ... please! -- if you didn't know so well the source from which it springs.

One of the biggest mouths in all of sports.

And while we're on this tip, because "Rumble, young girl, rumble" -- in addition to being a touching homage and a clever flip of the script -- is a line you hope every daughter you have and every little girl you know commits to memory and whispers like a mantra before every single game, test, and trial of her life.

And lastly, because they get the details right. For example: There is a moment about four shots into the spot where the producers wanted a floor-level take on Ali's boots. Problem was, they didn't have that angle in the stock footage, so it was going to have to be a new live-action bit done by the body-double. Plus, they didn't have the same adidas boots Ali wore in '67. No longer made.

So you fake it and figure nobody'll notice, right? Go with something similar, right?

No. You get the boots remade to exact specifications and fly them in for the shoot.

Note: In the interest of full disclosure, I should say that adidas does some advertising on this-here Web site. In the interest of further disclosure, I should say that "Ali vs. Ali" is one of a series of "Impossible is Nothing" ads, including another which is out now, featuring Muhammad Ali taking a morning run with some of the world's top contemporary athletes, and three others featuring similar technology still to come.